Coloring ring back tone service is a value-added service in communication service, and it renders a calling party able to listen to the coloring ring back tone, such as a piece of music, which is customized by the called party during call waiting.
The coloring ring back tone service can be realized in many ways, for example, Chinese Application No. 03113374.6 provides a method for realizing coloring ring back tone by employing intelligent network, which is specifically as follows: when a calling party makes a call, a calling/called switch triggers an intelligent network service (i.e. a first intelligent network service), and the first intelligent network service instructs the calling/called switch to connect the call to an intelligent peripheral, then the intelligent peripheral triggers a coloring ring back tone service (i.e. a second intelligent network service), and the coloring ring back tone service instructs the intelligent peripheral to connect to the called party, meanwhile displays the coloring ring back tone to the calling party.
In this method, when the first intelligent network service instructs the calling/called switch to connect the call to the intelligent peripheral, it is likely to rise a problem that the called party cannot be connected, since the relay from the switch to the intelligent peripheral is occupied, the out relay of the intelligent peripheral is occupied, or the intelligent peripheral fails in triggering service. If such a problem arises, for a user, it means the user has applied for a new service, but the completing rate declines, which incurs users' dissatisfaction about telecom service. Hence, the above mentioned problem can be solved if the protection of incoming calls in coloring ring back tone service can be realized, however, no technical documents describing such similar technical solution have been found.